Doxorubicin (adriamycin) was administered to 35 children with malignant solid tumors to further evaluate its usefulness and toxicity. Two dosage schedules were used: 25 mg/sq m of body surface area weekly, and 25 mg/sq m on two consecutive days and then every two weeks. The agent produced tumor regression in 17 children; the tumors included osteosarcoma, neuroblastoma, Wilms tumor, reticulum cell (histiocytic) lymphoma, and hepatoblastoma. Toxic reactions including alopecia, hematopoietic depression, vomiting, mucosal ulcerations, and weight loss were similar with each schedule. Administration of doxorubicin in a dosage of 50 mg/sq m at two-week intervals allows time for detection of toxic reactions and evaluation of tumor response before administration of subsequent doses.